1. Field of the Invention
The present invention relates to methods and systems for a call set-up in a mobile communication terminal, and more particularly to methods and systems for a call set-up in a mobile communication terminal adapted to perform a call set-up through a binary Session Initiation Protocol message (SIP message) of short data burst (SDB) when setting up a call using a SIP in the terminal.
2. Description of the Prior Art
In general, a SIP is a text-based protocol used to provide services such as instant message service, Push to Talk (PTT), picture phone, picture conference and the like which are applied to a mobile communication terminal. The SIP can be used to invite a user to all types of sessions including multicast session and point-to-point session. Since the SIP is a text-based protocol, it has advantages that a user can easily comprehend it and it has an easy extensibility. However, since there are no limitations in size and standard, its data capacity is generally large.
In a SIP-based service, a call set-up process passing through nodes such as base stations and switching apparatuses or servers is carried out using a traffic channel. In the call set-up process using the traffic channel, the call set-up is delayed until the traffic channel is activated, thereby causing inconveniences to a user of a mobile communication terminal.
FIG. 1 is a block diagram showing a structure of a network for a call set-up between mobile communication terminals. The network for a call set-up between mobile communication terminals may comprise a call-originating terminal 11 trying a call set-up, call-originating base station and proxy server 12, a session resource, i.e., a group talk server (GTS) 13 managing a traffic channel and maintaining and managing a call connection, call-incoming base station and proxy server 14 and a call-incoming terminal 15 receiving a request of the call connection.
A method for a call set-up between the mobile communication terminals in the network having the above structure is described with reference to FIG. 2.
First, the call-originating terminal 11 having logged on a point-to-point protocol (PPP) tries an origination to start a traffic channel set-up, under dormant state (S202). After completing the traffic channel set-up, it tries an invite for a call set-up with the call-incoming terminal 15 (S204).
The invite message transmitted from the call-originating terminal 11 is a message of a standard full SIP type and is transmitted to the call-originating base station and proxy server 12 through the traffic channel. At this time, when the traffic channel is activated (it takes about 4˜5 seconds), the call-originating terminal 11, which has stood by under dormant state, transmits the invite message to the call-originating base station and proxy server 12 using the activated traffic channel (S204).
The call-originating base station and proxy server 12 having received the invite message routes the invite message to the GTS 13 (S206).
The GTS 13 allots a resource (i.e., traffic channel) regarding the invite of the call-originating terminal 11, and identifies subscriber information of the call-incoming terminal 15 existing in the invite message, and then routes the invite message to the call-incoming base station and proxy server 14 (S208).
The call-incoming base station and proxy server 14 transmits a page to the call-incoming terminal 15 so as to transmit the invite message to the call-incoming terminal 15 standing by under dormant state (S210).
When the call-incoming terminal 15, which is standing by under dormant state, receives the page from the call-incoming base station and proxy server 14, it tries an origination (i.e., a response to the page) so as to process the received page (S212) and is transitioned to the traffic channel activated state. In this case, it takes about 4˜5 seconds for the call-incoming terminal 14 to be transitioned from the dormant state to the traffic channel activated state.
When the traffic channel is transitioned to the activated state, the call-incoming terminal 15 receives the invite message of the standard full SIP type from the call-incoming proxy server 14 and transmits a response message to the invite message under state that the traffic channel is activated (S214).
The response message transmitted from the call-incoming terminal 15 is transmitted to the call-originating terminal 11 through the traffic channels under activated state between the call-originating terminal 11 and the base station 12, and between the call-incoming base station 14 and the call-incoming terminal 15 (S214˜S220).
The call-originating terminal 11 having received the response message transmits a SIP acknowledgement message to the call-originating base station and proxy server 12 (S222) which in turn transmits the SIP acknowledgement message to the GTS 13 (S224). Then, data transmission is made between the call-originating terminal 11 and the call-incoming terminal 15 through a real-time transport protocol (RTP).
Like this, according to the method for a call set-up between the mobile communication terminals of the prior art, in case that the call-originating terminal 11 tries the call set-up under PPP dormant state that the wireless resource (i.e., traffic channel) is not actually activated, the call-originating terminal 11 does not transmit the invite message until the traffic channel is activated from the dormant state. In addition, in case that the invite message is transmitted to the call-incoming terminal 15 after being routed between the servers, the call-incoming terminal 15 is transitioned to the traffic channel activated state from the dormant state after receiving the page. Like this, it is not possible to freely transmit/receive the final response and media data between the call-originating terminal 11 and the call-incoming terminal 15 until the traffic channel of the call-incoming terminal 15 is activated.
In other words, the method for a call set-up between the mobile communication terminals according to the prior art is a call set-up method using a traffic channel wherein the call set-up is delayed by a time required for each of the call-originating terminal and the call-incoming terminal to be transitioned to the traffic channel activated state from the dormant state. Accordingly, at least 10 seconds may be delayed until the call set-up is actually made, thereby causing considerable inconveniences to a user of a mobile communication terminal. In addition, there may occur a problem in activation of a service itself.